Structure and thermal expansion behavior of Y2−xLnxMo4O15Y2−xLnxMo4O15 (Ln=NdLn=Nd, Dy)

Two new series of rare earth solid solutions of Y2−xNdxMo4O15Y2−xNdxMo4O15 (x=0.0–0.4x=0.0–0.4) and Y2−xDyxMo4O15Y2−xDyxMo4O15 (x=0.0–2.0x=0.0–2.0) were prepared successfully and studied by X-ray and neutron powder diffractions. All these molybdates crystallize in a monoclinic space group P21/cP21/c. The lattice parameters a, b and c   of Y2−xLnxMo4O15Y2−xLnxMo4O15 increase linearly with increasing neodymium and dysprosium content. The framework of Y2−xNdxMo4O15Y2−xNdxMo4O15 is very similar to that of ZrW2O8ZrW2O8. The O14 belonging to the Mo(1)O4 tetrahedron is weakly connected to the Mo(2) of the Mo2O7 group in Y2−xNdxMo4O15Y2−xNdxMo4O15, which is similar to the O3 of the W(2)O4 tetrahedron connecting to the W(1) of W(1)O4 tetrahedron in the ZrW2O8 structure. The temperature dependence of Mo(2)O14 bond distance seems to dominate the thermal expansion behavior of Y2−xNdxMo4O15Y2−xNdxMo4O15.

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